The present invention relates to a dust-boot for a booster used in a vehicle, more particularly, to an improved dust-boot provided with a noise preventing (when air is sucked) wall of plate type.
It is widely practiced to employ a vacuum booster (hereinafter simply called booster), as a sort of servomechanism, for getting a strong braking force under a light braking operation. When this booster, partly projecting into the cabin, i.e., projecting from the dash-panel into the driver's room, is actuated, rapidly sucked air through the air-sucking hole (or holes), which is formed in the dust-boot covering the above-mentioned projected portion of the booster, produces a kind of intermittent sucking noise. This noise caused by an eddy turbulence of air is directly delivered to the driver, without being damped, to his great disagreeableness, because the noise source is exposed, without any cover, to the driver's ears.
As a countermeasure against this noise problem, provision of silencers made of a layer of various fibers, and of air cleaners made of filter paper, filter cloth, etc., inside the air-sucking hole(s), has been tried with no satisfactory results.
The reason for this problem having been closed up resides in that the size of the booster has gradually been enlarged for enhancing the performance of the brake system and for decreasing the brake pedal depressing force. It can be well understood that the volume of air sucked rapidly increased in consequence, bringing about the increase of the noise, and on the other hand the driver's assessment for the noise prevention effects has become sensitive.